Adherence to CPAP in Randomized Controlled Trials in Obstructive Sleep Apnoea-A Meta-Analysis and Investigation of...

Background: Continuous positive airway pressure (CPAP) is the most effective treatment for obstructive sleep apnoea (OSA). However, CPAP adherence in randomized controlled trials (RCTs) is frequently inadequate, potentially leading to an underestimation of the therapy's true effect on relevant outcomes. The aim was to identify patient and study characteristics that predict adherence to CPAP therapy in RCTs. Methods: PubMed and the existing meta-analyses were searched (1984 to 31 December 2024). A study-level meta-analysis of RCTs comparing CPAP with inactive control in patients with OSA was conducted. Meta-regressions and subgroup analyses (<4 h vs. ≥5 h usage) were undertaken to identify the predictors of CPAP adherence. Risk-of-bias was assessed using the Cochrane RoB-2 tool. Results: In 136 RCTs reporting on CPAP use, including 8827 patients with OSA (55 [49.5-59.8] years, 77.4 [61.2-89.2]% male, BMI 31 [28.9-33.2] kg/m², Epworth Sleepiness Scale (ESS) 10.0 ± 2.8, apnoea-hypopnoea-index (AHI) 35.7 ± 13.4/h), mean nocturnal CPAP use was 4.5 ± 1 h. CPAP use of ≥4 h, ≥5 h, and ≥6 h per night was observed in 71.3%, 34.1%, and 7.8% of RCTs, respectively. Higher baseline AHI was the strongest predictor of longer CPAP use in meta-regressions (p < 0.001, β = 0.02, 95% CI 0.01-0.04). Baseline AHI was also significantly higher (40.3 ± 12.8 vs. 29.9 ± 12.6) in the ≥5 h vs. <4 h subgroup (p < 0.01, large effect size d = 0.84). A higher nightly CPAP usage was more likely in smaller (p < 0.05, d = 0.45) and single-centre trials (p < 0.05, h = 0.52). Sex distribution, age, BMI, ESS, and follow-up had no significant effect on nightly CPAP use. Conclusions: Higher baseline AHI independently predicted longer CPAP use in RCTs, while sleepiness and demographics did not. This study was registered at PROSPERO (CRD420250653394) and received no external funding.